The hadrosaurids come in two basic
varieties; hollow-crested and non-hollow-crested. At each of these levels, there are
several groups, but this page will not cover them, because there is quite a bit of
housekeeping to do before we get there, namely, slogging through the indeterminate
members (interestingly, once a piece of petrified wood was described as being
hadrosaurid remains [Aachenosaurus]). If you want to skip this page, I don't blame
you (although I have a soft spot for Claosaurus; it was one of the first
obscure dinosaurs I learned about, back around the late 1980s-early 1990s, from
an article in a kid's magazine about dinosaurs).
Additional basal hadrosaurid material is known from the late
Santonian (LK) of Italy, the mid Turonian (LK) of Alaska, late
Maastrichtian (LK) of Spain and possibly Antarctica. In addition, a
hadrosaurid femur discovered in New Mexico may be evidence that some dinosaurs
were able to make it into the earliest part of the Paleocene, just beyond the
K-T boundary, although most authorities consider it to have been reworked from
older sediments.
From the early 1980s into the first decade of the 21st
century, the standard model for ornithopod chewing involved a system of skull
bones with flexible joints, the upshot being that the maxillae
pivoted inward during chewing to grind things. More advanced computer modeling
now allows this to be tested in finer detail, and it appears that, instead, the
lower jaws were moving to permit grinding, with a combination of fore and aft
motion and rotation of the two halves of the lower jaw (joined loosely at the
front by the predentary) along their long axes.
In addition to mobile jaw bones, hadrosaurids were amply
equipped with teeth. The old kids' books say 2,000, but this is an overestimate;
about 1,600 is the most that has been reliably estimated, and lambeosaurines had
fewer than half of that total, perhaps 700 at most. Still, this is significantly
more than you or I could be reasonably expected to exhibit. Because these teeth
were distributed in columns of three to six teeth, most of them were not in use,
and would only come into play when the tooth above had been shed; the animals
had more or less a conveyor belt of teeth. Furthermore, the teeth were composed
of six different tissues (mammals have four), with varying hardnesses, and as
teeth wore down, different tissues became more or less prominent. This is an
excellent way to promote specialization and differentiation of species, and
early results indicate that different groups of hadrosaurids used their
elaborate dentitions differently, with at least some lambeosaurines emphasizing
grinding, and saurolophinids emphasizing slicing.

Hadrosauridae: Hadrosaurids were long thought to have lived in
water, another set of victims of the mindset that condemned sauropods as well to the watery
regions. In the case of hadrosaurids, they were they because they were supposedly
swimmers, as shown by their tall tails and "webbed" hands found on
"mummies," and because their teeth seemed weak However, it turned out the
tail was very inflexible due to bony tendons, and the webs of the hands were shown to be
dried-out cushions for the hands. As for the teeth, that is a patent lie. Hadrosaurids were very well adapted to feed at low levels on land, much like
bison. Their backs
even show a striking resemblance to the way bison spines are curved. The best
analogue for a hadrosaurid would have to include this low-browsing ability with a hint of
the bewildering variety of display devices hadrosaurids were equipped with. Many
hadrosaurids are known to have lived in groups, possibly not true herds, but groups
nonetheless. In fact, it has been suggested that one mass "grave" of Maiasaura
contains the remains of a gathering 10,000 individuals strong.
Hadrosaurids show some sort of unusual midline
spinal phenomenon. Some appear to have dragon-like rectangular nonbony segments
running down the midline of the back, while others suggest a deep, horse-like muscular
neck. Hadrosaurids appear to have had rather thin, leathery skin, with large
polygonal or oval tubercles surrounded by many smaller ones. The scale
patterns may have some diagnostic value.
It is an unfortunate fact that without a decent
skull, it is difficult to differentiate most hadrosaurids, due in part to the basic overall
similarity of the skeletal plan, and in part to the relative lack of attention
given to hadrosaurid postcrania. Lambeosaurines can be told from saurolophines
in
some elements, such as the hip bones and height of the neural spines (many lambeosaurines
have slight "sails" down the back), but that is about as far as one can go with
separating hadrosaurids from postcranial material at this point; people are
looking for differentiating characters, though. Ceratopsids
have a similar problem, but probably worse, as the frill is necessary as
everything else is pretty much the same across taxa, and the frill didn't come
in until the animal was nearly an adult.

Based on a mostly complete postcranium, Claosaurus
is one of the most primitive hadrosaurids. However, this is a good
place to explode the myth of it retaining the first metatarsal, which all other hadrosaurids for which the foot is known have
lost. There was no MT I!

Hadrosaurus foulkii Leidy, 1858

early-middle Campanian (LK) of New Jersey

Sadly, this historically important genus is based on
remains that do not include a good skull. It is known mostly from a partial postcranium (more would have
been known if people had known about dinosaurs in the 1830s and had kept
the bones together, but that's life), and traditionally it has been
thought of as like Gryposaurus or Kritosaurus, although
this cannot be established. This was the first
classic dinosaur to be known from a decent postcranium, and through the limb
proportions showed early researchers that some dinosaurs were bipedal.

Lophorhothon atopus Langston, 1960

Campanian (LK) of Alabama and North Carolina

A rare Southeastern iguanodontian (heck, rare
Southeastern dinosaur!), Lophorhothon is
based on a partial skull and skeleton from a juvenile animal. The skull has a small
pyramidal crest between the eyes. In the past, this animal was interpreted as a basal
"saurolophinid", but new research has suggested both that it
actually may be closer to Tenontosaurus, or that it is a basal saurolophine.

Plesiohadros is known from
skull and postcranial remains, representing a basal hadrosauroid/hadrosaurid-type
animal (although note that it is apparently bad paleontological karma to
give a genus a name suggesting it is near the base of the hadrosaurid
radiation; see Eolambia and
Protohadros). It is of note for being one of the few ornithopods
known from the Djadokhta Formation, better known for almost everything but
ornithopods.

Shuangmiaosaurus gilmorei
You, Ji, Li J., and Li Y., 2003

Cenomanian-Turonian (LK) of China

Described as the sister taxon to
Hadrosauridae, Shuangmiaosaurus is based on partial remains of the
upper and lower jaws.

Tethyshadros insularis Dalla Vecchia,
2009

late Campanian-early Maastrichtian (LK) of
Italy

At last, the hadrosaurid formerly known as
"Antonio" is described (hadrosauroid if Hadrosauridae is
restricted to Lambeosaurinae and Saurolophinae, Hadrosauridae using the
definition that includes Telmatosaurus). I was pleased to
learn that several other individuals are known as well, from the same
sedimentary lens. It becomes the second classic dinosaur to be named
from Italy, after Scipionyx.
Reconstructions are of course not as good as seeing the real thing, but on
the other hand if you've seen enough reconstructions, you begin to get a
feel for proportions and such (or perhaps that's just me). One of my
pastimes as a kid back in the 1980s was tracing the skeletons from The
Illustrated Encyclopedia of Dinosaurs, and so I've long liked going to
the big picture. In this case, turning to the reconstruction of the
lovely articulated and nearly complete type (the layout as found vaguely
echoes a Bernissart Iguanodon), I am struck by several things. Starting up front, the skull is quite large, with
impressively large infratemporal fenestrae, and
similar in build to the gracile iguanodont Mantellisaurus. There is no gryposaur-like nasal
arch, unlike some early reports (probably a bone was jogged out of place).
Going farther back, the tibiae are very long compared to the
thighs, and the ischia extend back into yesterday. There is also
something interesting with the hand. It takes a few moments, but
then it becomes clear: there is no little finger. Unlike other
hadrosaurids which had digit V hanging out beyond the II-III-IV column, Tethyshadros
made do without that extra manipulator. Checking the diagnosis, I'm
doing quite well, as all of these are deemed autapomorphic. Of
course, in this case the dinosaur made it easy; I doubt I'd do so well
with a troodontid, for example.

Zhanghenglong is a transitional
iguanodont-hadrosaurid based on
a partial skull. Material including part of the anterior torso of a smaller
individual is also known. The jugals are deep, giving it fairly droopy
"cheeks", and the neural spines are on the long side. The forearms are
proportionally long and slender.

Hadrosauridae i.s.:

Taxon or Taxa:

Time/Place:

Comments:

Cionodon arctatus (N.D.)
Cope, 1874 (?Thespesius)

late Maastrichtian (LK) of Colorado

This indeterminate hadrosaurid is
based on a maxilla, two dorsals, partial third metatarsal, and the ends of
an ulna.

"Cionodon" stenopsis (N.D.) Cope,
1875

late middle-early late Campanian (LK) of Alberta

This is an anonymous indeterminate hadrosaurid from the
early days of North American dinosaur research, based on part of a maxilla.

"Claosaurus affinis"
(N.N.)
Wieland, 1903

early Campanian (LK) of South Dakota

This animal is based on toe bones, which
became mixed-up with a toe bone from C. agilis. They are
mostly of interest for documenting the presence of hadrosaurs living at
this time in the vicinity of the Western Interior Seaway.

Diclonius: (N.D.) Cope,
1876

D. pentagonus (N.D.) (type) Cope,
1876

middle-late Campanian (LK) of Montana

Because the teeth
(and one partial lower jaw, from D. pentagonus) these various species are
based on all came from the same area, they are retained in Diclonius.
They
may very well all belong to the same animal, or from a collection of Judith
River hadrosaurids.

D. calamarius (N.D.) Cope,
1876

D. perangulatus (N.D.) Cope,
1876

Glishades ericksoni
(N.D.) Prieto-Márquez, 2010

Campanian (LK) of Montana

Glishades is based on two partial
premaxillae from the Two Medicine Formation. It was described as a derived hadrosauroid,
but not a true hadrosaurid, possibly related to Bactrosaurus. More
recent research indicates that it is a juvenile hadrosaurid, possibly a
saurolophine.

"Hadrosaurus":

"H." breviceps (N.D.) Marsh,
1889

middle-late Campanian (LK) of Montana

This is just another indeterminate
hadrosaurid, possibly the same as Prosaurolophus, although it has
been referred to Kritosaurus (in the guise of Gryposaurus)
in the past. It is based on part of a dentary.

"H." cavatus (N.D.) Cope, 1871

late Campanian-early Maastrichtian
(LK) of New Jersey

These two species may well be the same
thing. "H." cavatus is based on caudal vertebrae, "H."
minor on dorsals, with referred material comprised of a partial hindlimb,
verts, ribs, and hips. The [currently missing] ischia are described
as unexpanded, possibly indicating a saurolophine.

"H." minor (N.D.) Marsh, 1870

late Campanian-early Maastrichtian (LK) of New Jersey

Hypsibema crassicauda (N.D.)
Cope, 1869

Campanian (LK) of North Carolina

Hypsibema is a gigantic hadrosaurid
based on caudals, a partial humerus, a partial tibia, and a partial
metatarsal. The species "Neosaurus" missouriensis, another giant hadrosaurid from the eastern part of the United States,
is sometimes assigned to Hypsibema, but
given the limited remains, I don't find that justified. The original
material also mixed in a theropod femur for good measure.

"Jaxartosaurus" fuyunensis (N.D.)
Wu, 1984

LK of China

This indeterminate (or possibly not even
described) hadrosaurid could be a lambeosaurine.

Lapampasauruscholinoi
Coria, González-Riga, and Casadio, 2013

late Campanian-early Maastrichtian (LK) of
Argentina

Lapampasaurus appears to be known from
material including at least cervicals, shoulder girdle bones, and toe
bones.

Microhadrosaurus nanshuingensis (N.D.)
Dong, 1979

early Maastrichtian (LK) of China

Based on a small dentary, this is most probably a juvenile
hadrosaurid.

This dubious giant hadrosaurid
may masquerade as either Parrosaurus (because Neosaurus was
preoccupied) or as Hypsibema missouriensis (or even H.
crassicauda, as I used to have it); as the latter, it is most commonly
seen, and has become the official state dinosaur of Missouri. "Neosaurus"
is based on caudals, at first thought to belong to
a camarasaurid-like sauropod because of their
large size. A few other fossils have since been uncovered, including
jaw material.

Ornithotarsus immanis (N.D.)
Cope, 1869 (?Hadrosaurus)

Campanian (LK) of New Jersey

Sometimes synonymized with Hadrosaurus, this
animal is based on a partial hindlimb of a very large individual.

?Orthomerus dolloi (N.D.)
Seeley, 1883

Maastrichtian (LK) of the Netherlands

Often considered the same as Telmatosaurus in
older works, this animal may not even be a hadrosaurid.

Pteropelyx is usually thrown out as a
synonym of Corythosaurus, and then ignored because the type has no
skull and it would have priority over Corythosaurus of several
decades. It is known from a collection of postcranial remains. Almost no one has talked about Pteropelyx since Lull and Wright in
1942, or has taken it seriously as a useful name since Lambe in 1902 (who
thought it to be a subgenus of Trachodon). Interestingly, for
a supposed synonym of a lambeosaurine, it is described as having slender
ischia, which is more of saurolophine thing.

This indeterminate hadrosaurid
used to get a lot more play (if you go back in the literature, a bunch of
species now referred to Edmontosaurus were put here). It is
based on caudals and a pedal phalanx.

Trachodonmirabilis
(N.D.) Leidy, 1856

middle-late Campanian (LK) of Montana
and Alberta

Made famous in countless cheesy children's
toys, Trachodon is actually a fraud, a dubious tooth taxon. In fact, of the
type teeth, some belong to a ceratopsid, and others to a hadrosaurid. The name today
is usually restricted to the hadrosaurid teeth, which may have come from an animal like Corythosaurus.

"Trachodon":

"T." altidens (N.D.)
Lambe, 1902

middle-late Campanian (LK) of Alberta

Based on a partial maxilla, this
specimen has been mooted as a "procheneosaur", which for our
purposes means a juvenile lambeosaurine, which it may well be.

"T." marginatus (N.D.)
Lambe, 1902

middle-late Campanian (LK) of Alberta

This collection of postcranial
remains and teeth has sometimes been referred to Kritosaurus (as Gryposaurus),
although a chunk of it has ended up in Lambeosaurus. It
probably represents Gryposaurus.

"T." selwyni (N.D.)
Lambe, 1902

This species is based on a lower
jaw with teeth, the latter most like those from "Hadrosaurus" breviceps.
It seems to be most like Gryposaurus and Lambeosaurus.

"Troodon" isfarensis (N.D.)
Nesov,
1995

early Santonian (LK) of Tajikistan

This was described as a troodontid
based on a frontal (currently missing), but more recent study using the
description and photograph of the bone shows that it was really a
hadrosaurid, based on a prefrontal.

Saurolophinae and Lambeosaurinae: These two groups are the derived hadrosaurids.
They have some of the best fossil records of any dinosaurs, with skulls and
skeletons known for most taxa.